'Legends of Tomorrow' season 2 spoilers, plot news: Vixen joins the hero lineup, new big bad brings more trouble to the team

The CW's popular action-adventure series "Legends of Tomorrow" will have a new addition to its superhero lineup once the series returns for its sophomore run later this year.
Vixen will join the cast, but there's a catch: Megalyn E.K. will not be portraying her. The actress gave life to Vixen for a stint in "Arrow," and she also voiced the role in an animated spinoff series. However, due to other commitments, E.K. will not be able to play the role of Vixen. Casting is currently underway for another actress to replace her, but the network is not closing its doors if E.K. wants to reprise her role.
The big bad in season 2 has yet to be named, but according to executive producer Marc Guggenheim, the new villain is greatly different from the Thanagarians. "All I'll really say about the nemesis in season two is Vandal Savage looks like a walk in the park compared to what the Legends will be facing.," he explained. "This will be a much, much bigger threat. I'm going to leave it at that because when we do reveal it, it's going to be pretty big. People will be asking, 'Vandal who?' once they get the full picture of what our team is up against. It's going to be way bigger than what you can even imagine, I can guarantee it."
As for the second season's premise, executive producer Phil Klemmer plans to approach it in another perspective and set it apart from the freshman season. "... [The first episode of season two] will very much be a new pilot with new good guys, new bad guys, new stakes, new dynamics, new goals. The team will basically have to find a new purpose," he hinted.
The network has yet to announce a definitive premiere date for "Legends of Tomorrow" season 2, but it is expected to begin airing sometime in the Fall.